President Bush, currently on a visit to Kiev, told journalists following a meeting with Ukrainian President Viktor Yushchenko, that: "Russia could easily overwhelm the missile defense systems that we have envisioned."
George Bush, who arrived in Ukraine late Monday, said he had told and would tell Russian President Vladimir Putin during an upcoming NATO summit that missile defense elements will be aimed at repelling threats from the Middle East and not at Russia.
He also said that both countries needed to work together: "It's in his [Putin's] interest that we participate in sharing information - a missile from the east can fly north just as easily as it can fly west."
The U.S. intends to deploy 10 interceptor missiles in Poland and a radar in the Czech Republic citing a threat from Iran and other "rogue states," while Russia views these plans as a destabilizing factor for Europe and a threat to its national security.
George W. Bush is due to attend a NATO summit in Bucharest, Romania April 2-4, before meeting with Russia's President Vladimir Putin over the weekend in the Black Sea resort of Sochi for the last time before Putin leaves his post.
Recently, there has been some progress in the long-running dispute between the two countries over the missile defense issue.
During their visit to Moscow in late March, U.S. Defense Secretary Robert Gates and Secretary of State Condoleezza Rice offered to let Russia monitor the proposed U.S. missile and radar bases in Central Europe.
Washington has also offered not to activate the system until there is a "clear and present" threat from Iran or other potential adversaries.
"I think we're moving in a direction...where Russia and the United States could have missile defense as an area of strategic cooperation," National Security Advisor Steve Hadley told reporters Monday.
However, he said the U.S. and Russia may not resolve their European missile shield dispute at the upcoming meeting in Sochi, but will continue working on the issue.
"An issue about how Russia might fit and cooperate and be a part of those efforts, that probably is for Sochi or later - it may not get done by Sochi. There's no deadline here," Hadley said.
Russia's Foreign Minister Sergei Lavrov praised last week U.S. moves to ease Russian missile shield concerns, but said giving up the idea of opening new missile bases in Central Europe was the best way of addressing Moscow's unease.